Nearctic realm
The Nearctic realm is one of the eight biogeographic realms constituting the Earth's land surface.
For the thoroughbred racehorse, see Nearctic (horse).The Nearctic realm covers most of North America, including Greenland, Central Florida, and the highlands of Mexico. The parts of North America that are not in the Nearctic realm include most of coastal Mexico, southern Mexico, southern Florida, coastal central Florida, Central America, and the Caribbean islands. Together with South America, these regions are part of the Neotropical realm.
History[edit]
Although North America and South America are presently joined by the Isthmus of Panama, these continents were separated for about 180 million years, and evolved very different plant and animal lineages. When the ancient supercontinent of Pangaea split into two about 180 million years ago, North America remained joined to Eurasia as part of the supercontinent of Laurasia, while South America was part of the supercontinent of Gondwana. North America later split from Eurasia. North America has been joined by land bridges to both Asia and South America since then, which allowed an exchange of plant and animal species between the continents, the Great American Interchange.
A former land bridge across the Bering Strait between Asia and North America allowed many plants and animals to move between these continents, and the Nearctic realm shares many plants and animals with the Palearctic. The two realms are sometimes included in a single Holarctic realm.
Many large animals, or megafauna, including horses, camels, tapirs, mammoths, mastodons, ground sloths, sabre-tooth cats (Smilodon), short-faced bears and the American cheetah, became extinct in North America at the end of the Pleistocene epoch (ice ages) in what is called the Quaternary extinction event.